Allen-Bradley Logix5000 Reference Manual page 484

Chapter 11 Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)
Continuous task
If Initialize_Task_1 = 1 then
The ONS instruction limits the execution of the EVENT instruction to one scan.
The EVENT instruction triggers an execution of Task_1 (event task).
Task_1 (event task)
The GSV instruction sets Task_Status (DINT tag) = Status attribute for the event task. In the Instance Name attribute, THIS
means the TASK object for the task that the instruction is in (that is, Task_1).
If Task_Status.0 = 1 then an EVENT instruction triggered the event task (that is, when the continuous task executes its EVENT
instruction to initialize the event task).
The RES instruction resets a counter that the event task uses.
The controller does not clear the bits of the Status attribute once they are set. To use a bit for new status information, you must
manually clear the bit.
If Task_Status.0 = 1 then clear that bit.
The OTU instruction sets Task_Status.0 = 0.
The SSV instruction sets the Status attribute of THIS task (Task_1) = Task_Status. This includes the cleared bit.
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Example 2:
The following example uses an EVENT instruction to initialize an event task.
(Another type of event normally triggers the event task.)
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011